lcx_ecdh.h

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ECDH (Elliptic Curve Diffie Hellman) key exchange. More...

Functions
cx_err_t	cx_ecdh_no_throw (const cx_ecfp_private_key_t *pvkey, uint32_t mode, const uint8_t *P, size_t P_len, uint8_t *secret, size_t secret_len)
	Computes an ECDH shared secret. More...
static int	cx_ecdh (const cx_ecfp_private_key_t *pvkey, int mode, const unsigned char *P, unsigned int P_len, unsigned char *secret, unsigned int secret_len)
	Computes an ECDH shared secret. More...

Detailed Description

ECDH (Elliptic Curve Diffie Hellman) key exchange.

ECDH is a key agreement protocol that allows two parties to calculate a shared secret over an insecure channel. The public and private keys are elements of a chosen elliptic curve.

Function Documentation

cx_ecdh()

static int cx_ecdh ( const cx_ecfp_private_key_t *  pvkey, int  mode, const unsigned char *  P, unsigned int  P_len, unsigned char *  secret, unsigned int  secret_len  )

Computes an ECDH shared secret.

Depending on the mode, the shared secret is either the full point or only the x coordinate. This function throws an exception if the computation doesn't succeed.

Warning

It is recommended to use cx_ecdh_no_throw rather than this function.

Parameters

[in]	pvkey	Private key. Shall be initialized with cx_ecfp_init_private_key_no_throw.
[in]	mode	Crypto mode flags. Supported flags: CX_ECDH_POINT CX_ECDH_X
[in]	P	Pointer to the public key encoded as 04 || x || y: x and y are encoded as big endian raw values and have a binary length equal to curve domain size.
[in]	P_len	Length of the public key in octets.
[out]	secret	Buffer where to store the shared secret (full or compressed).
[in]	secret_len	Length of the buffer in octets.

Returns

Length of the shared secret.

Exceptions

CX_INVALID_PARAMETER

INVALID_PARAMETER

CX_EC_INVALID_CURVE

CX_MEMORY_FULL

CX_NOT_LOCKED

CX_EC_INVALID_POINT

CX_INVALID_PARAMETER_SIZE

CX_EC_INFINITE_POINT

cx_ecdh_no_throw()

cx_err_t cx_ecdh_no_throw	(	const cx_ecfp_private_key_t *	pvkey,
		uint32_t	mode,
		const uint8_t *	P,
		size_t	P_len,
		uint8_t *	secret,
		size_t	secret_len
)

Computes an ECDH shared secret.

Depending on the mode, the shared secret is either the full point or only the x coordinate.

Parameters

[in]	pvkey	Private key. Shall be initialized with cx_ecfp_init_private_key_no_throw.
[in]	mode	Crypto mode flags. Supported flags: CX_ECDH_POINT CX_ECDH_X
[in]	P	Pointer to the public key encoded as 04 || x || y: x and y are encoded as big endian raw values and have a binary length equal to curve domain size.
[in]	P_len	Length of the public key in octets.
[out]	secret	Buffer where to store the shared secret (full or compressed).
[in]	secret_len	Length of the buffer in octets.

Returns

Error code:

• CX_OK on success
• CX_INVALID_PARAMETER
• INVALID_PARAMETER
• CX_EC_INVALID_CURVE
• CX_MEMORY_FULL
• CX_NOT_LOCKED
• CX_EC_INVALID_POINT
• CX_INVALID_PARAMETER_SIZE
• CX_EC_INFINITE_POINT

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